The present invention relates generally to locomotive display and more specifically to a method of determining maximum service brake reduction and its use with, for example, a Locomotive Engineers Assist Display and Event Recorder (LEADER) system.
The LEADER System, as described in U.S. Pat. No. 6,144,901, is a real-time, enhanced version of the Train Dynamics Analyzer (TDA), a long standing Locomotive Engineer training tool offered by the Train Dynamics Services Group of New York Air Brake. The LEADER system has the ability to display a real-time or xe2x80x9clivexe2x80x9d representation of a train on the current track, the trackage ahead, the dynamic interaction of the cars and locomotives (both head end and remote), and the current state of the pneumatic brake system. As a tool for the Locomotive Engineer, the LEADER system will allow insight into the effect of throttle changes and brake applications throughout the train providing feedback and information to the Locomotive Engineer not currently available. The information the LEADER system offers provides an opportunity for both safer and more efficient train handling leading to enormous potential economic benefits.
The LEADER System has all the necessary information to predict the future state of the train given a range of future command changes (what if scenarios). With this ability, LEADER can assist the railroads in identifying and implementing a desired operating goal; minimize time to destination, maximize fuel efficiency, minimize in train forces, (etc.) or a weighted combination thereof. LEADER will perform calculations based on the operational goal and the current state of the train to make recommendations to the Locomotive Crew on what operating changes will best achieve these goals.
The TDA functionality was enhanced to assist in training Locomotive Engineer how to better handle their trains. Designs of, simulators with math models are shown in U.S. Pat. Nos. 4,041,283; 4,827,438 and 4,853,883. Further capability was added to investigate accidents by playing the event recorder data through the TDA, monitoring critical physical parameters. Through the years data was collected from instrumented trains and laboratory experiments, allowing the models used by the TDA to be refined. On board data collection for off-loading is shown in U.S. Pat. Nos. 4,561,057 and 4,794,548.
As more Locomotive Engineers became familiar with the TDA display through training sessions, it became apparent that a real time version of the TDA in the cab of a locomotive would offer substantial benefits in improved train handling. Improved train handling would in turn foster safety and economic benefits. Technological limitations prevented the realization of LEADER for a number of years, but modern levels of computer processing power, decreased size of electronics, increase communication capability and increase size and readability of flat panel color displays has made the LEADER system a reality. Earlier designs for on board computer controllers is shown in U.S. Pat. No. 4,042,810 with a description of math models. The LEADER system provides safe and effective control of a train through display or control of the dynamically changing parameters.
The conventional air brakes and air brake systems in conventional freight trains, pneumatic storage reservoir on each freight car, called an auxiliary reservoir is charged by the brake pipe extending throughout the train. The compressor on the locomotive charges the brake pipe through a pressure regulating system. A brake application is achieved, following the charging action, by reducing the pressure in the brake pipe below the level of charge. When the brake pipe pressure is sufficiently reduced, the control valve on each car supplies air from the auxiliary reservoir to the car""s brake cylinder. The amount of air supplied is a function of the brake pipe reduction. During an application, if the reduced pressure in the reservoir becomes equal to the increased pressure in the brake cylinder, no further air flow will occur. The pressure is thus equalized and is referred to as equalization pressure. If brake pipe pressure is reduced below the equalization pressure for that individual car, no further brake cylinder pressure is achieved. Brake pipe pressure reduction below the equalization pressure are known as an xe2x80x9cover-reduction.xe2x80x9d This has the effect of wasting compressed air in the brake pipe increasing the time required to recharge the train brake system and release the brakes by the recharging. In actual freight operations, the brake pipe pressure that exists at each car may vary significantly with time and car location. It may take a very few minutes to charge the first car in a train to regulation level. It may take up to an hour or longer to charge the last car.
It is impossible for a locomotive engineer to calculate and keep track of the maximum reduction that can be made during brake applications. Thus the engineer can easily produce an over reduction wasting compressed air and increased time required to release and recharge the train brake system. This can result in a dangerous situation as often times a quick release and then recovery of the brake application is required to properly control the train. Thus there is a need for a system to inform the engineer when all cars have come to their equalization pressure and will achieve no additional braking for a further reduction of the brake pipe.
The present invention provides a method of determining the maximum brake pipe reduction including the steps of determining the status of the brake system throughout the train. The next step is determining, using the status of the brake system, maximum brake pipe reduction above which further reduction will not result in further brake application in the train. The determined maximum brake pipe reduction may be displayed or used to control the brake pipe. The status of the brake system throughout the train is determined by determining equalization pressure of the brake system in each car. This may be by a mathematical models or actual measurements. The equalization pressures are a function of pressures and volumes of the reservoir and brake cylinder of the individual cars.
The process can also include determining the minimum determined car equalization pressure throughout the train and determining the maximum brake reduction using the minimum determined car equalization pressure. If the minimum car equalization pressure for the train is greater than a first pressure value, the minimum equalization pressure is used to determine the maximum brake pipe reduction. If the minimum car equalization pressure is less than the first pressure value, the first pressure value is used in determining the maximum brake pipe reduction. The first pressure value is generally set to a minimum pressure required for an emergency operation of the brake system. Preferably the method is repeated after each brake pipe pressure increase. Recalculation is necessary because it changes the original dynamics and calculation of equalization pressure for each car.